The perinuclear theca (PT) is a proteinaceous shell that covers and protects the sperm nucleus. The long-term objective of this study is to elucidate the biological role during development and fertilization of proteins composing the PT of human sperm. Recent research in non-primates points to PT involvement in acrosome-nuclear docking, sperm-oolemma binding and oocyte activation. Its recognition and removal at an early stage of egg incorporation appears to be vital to the success of natural fertilization. If this initial interaction at the oocyte surface is omitted, as occurs in intracytoplasmic sperm injection (ICSI), the applicants hypothesize that the PT will persist and interfere with the normal decondensation of the sperm nucleus and jeopardize the success of embryos created by this method. Since human embryos cannot be created for research, an optimal model to study these presumed sperm PT-egg interactions is the non-human primate. Thus the specific aims are: 1) What is the molecular composition of the rhesus PT? The hypothesis to be tested is that the molecular makeup of rhesus monkey PT at least in part matches that of humans and also bears a resemblance with that of non-primates. Consequently, specific probes against rhesus homologs of PT proteins found in human will be raised, including specific antibodies and cDNAs. 2) The nature of rhesus PT protein expression and assembly during spermatogenesis and the interaction of PT with other developing sperm accessory structures will be determined. This aim using the probes described above should confirm that the morphogenesis of the rhesus sperm PT during spermiogenesis is required for the normal development of the sperm nucleus and accessory structures such as the acrosome. 3) The role of PT during natural and assisted fertilization in Rhesus will be determined. The hypothesis to be tested is that the Rhesus sperm is removed from the sperm nucleus at an early stage of fertilization where it induces the process of oocyte activation leading to the completion of oocyte meiosis and remodeling of the sperm nucleus into a male pronucleus. To support this hypothesis rhesus sperm PT-extracts, individual purified PT proteins and anti PT antibodies will be injected individually or as mixtures into fertilization-competent rhesus oocytes. The ultimate goal is to show proper PT processing during sperm-oocyte incorporation is vital to pronuclear development and early embryogenesis in primates.